Actuating cylinder



y 1944. D. H. BROWN 2,349,244

ACTUATING CYLINDER Filed Feb. 26. 1942 INVENTOR. DAVID M. BROWN Patented May 23, 1944 ACTUATING CYLINDER David H. Brown, North Hollywood, Calif., assignor, by mesne assignments, to Bendix Aviation, Ltd, North Hollywood, Calif., a corporation of California Application February 26, 1942, Serial No. 432,457

6 Claims. (Cl. 121-40) This invention relates to actuating cylinders and more particularly to actuating cylinders incorporating combined limit locks and dashpots.

Actuating cylinders are commonly used in air-.

planes as a motor means for moving various parts. For example, hydraulic cylinders are used on the landing gear of airplanes to extend or retract the landing gear. In such an operation, however, it is necessary to lock the landing gear in its retracted position and to lock the landing gearin its extended position so that there will be rigidity in either position. For this reason, it is common to provide actuating cylinders with limit locks, and as applied to landing gear cylinders and similar actuating cylinders these locks are referred to as uplocks and downlocks for the retracted and extended positions of the landing gear respectively.

Another feature present in the use of actuating cylinders is to reduce the movement of the actuated parts gradually near the end of the stroke of the actuating cylinder. The wheels and tires and attendant undercarriage for some airplanes weigh many hundreds of pounds and if this mass were retracted or extended rapidly and stopped instantaneously as the actuating cylinder reached the end of its stroke there would he impact stresses imposed upon the actuating cylinder and some parts of the undercarriage. For this reason it has been found desirable to provide some means for reducing the rate oi movement of actuating cylinders at the limits of their stroke. One such means which can be satisfactorily used with airplane actuating cylinders is a hydraulic dashpot or similar fluid metering device.

In the past, it has been common to use uplocks and downlocks associated with actuating cylinders, which locks were not an integral part of the actuating cylinder itself, and instead were.

combines the functions of a lock and a dashpot.

It is an object of the invention to provide an actuating cylinder with built-in or integral locks.

It is a further object of the invention to provide an actuating cylinder with locks so constructed that fluid under pressure does not flow to the cylinder until the locks are released.

Another object of the invention is to provide a cylinder with built-in or integral dashpots.

Still another object of the invention is to provide an actuating cylinder with a combined dashpot and lock structure.

It is an object of the invention to provide an actuating cylinder with built-in or integral dashpots and locks.

It is another object of the invention to provide an actuating cylinder having a dashpot construction resulting in a double metering action.

Still another object of the invention is to provide a cylinder with a lock pin having a pivotal mounting to the actuating parts for moving the same.

The drawing forming a part of this specification is an elevation view of an actuating cyl inder in full section, showingthe limit locks and dashpot construction formed integrally therewith.

Referring to the drawing. a cylinder it has flash-welded to its left end'a housing 12, and has threaded to its right end a housing 14. Placed within the cylinder it and p ssing through housings l2 and i4 is a piston and associated piston rod including a piston it having a fluid seal l8. To the left of piston Iii is a lockstep Ell and to the right of piston I6 is a lockstep 22. both having a round transverse cross section formed of machined pieces flash-welded together. Secured to the left lockst-ep 29 isa piston rod 24 having a elevis 25 threaded and secured thereto with a locknut 25. The adjacent housing i2 is provided with seals 38 to prevent leakage of hydraulic fluid. Flash-welded to the right lockstep 22 is a piston rod having a clevis 3A threaded there in and secured by a locknut 36. The adjacent housing M retains fiuid' seals 3% to prevent leakage of hydraulic fluid.

The left housing i2 is provided with a bore 48 coaxial with piston rod 26 and having a diameter slightly larger than the lockstep 2G. The upper part of housing l2 has a transverse bore 42 in which is placed a lock pin 44 secured by a pivot pin. 46 to as. Formed in the right side of lock pin M is a slot cooperating with a screw Ill to hold pin M in alignment. Threaded on stem 48 is a nut 58 which bears against a poppet valve element 52 when the stem 48 isin the upward or raised position shown. Poppet 52 is provided with a seal 5% to prevent leakage of fluid about stem 4e. Housing i2 is provided with a diagonal passage 5% leading from the left end of the housing to the transverse bore 42 at a point just -below a valve seat 58 for poppet 52. Branching from bore 42 just above poppet 52 is a hydraulic opening 53 acting as an inlet and outlet for hydraulic fluid depending upon the direction of movement of piston l6 within the cylinder Ill. The upper end of stem 48 is formed into a piston 60 and it will be noted that the area of piston 60 is larger than the area of poppet 52. Seals 62 on the upper part of piston 80 pre vent loss of fluid. Screwed on the top of housing I2 is a cap 64 compressing a coil spring 66 against the piston 84 urging it downwardly or in a direction to seat poppet .52 on itsseat 58. Protruding through cap 64 is a pin 88 secured to piston 60 and used for manually unseating poppet 52, or for operating a switch in a signaling circuit to indicate to the pilot.

The right housing [4 has a structure somewhat similar to left housing I2. with adjacent piston rod 32 and is slightly larger in diameter than the lockstep 22. A transverse bore 12 retains a lock pin 14 having axial passages l5 therethrough. Protruding upwardly from lock pin 14 is a stem '18 having a nut 80 secured therein for lifting a poppet 82 oil" of its seat 84 when the stem 18 is in the upward position shown. Just above poppet 82 is a hydraulic opening 86 acting as a hydraulic inlet and outlet depending upon the movement of piston l 6 within cylinder I8. Secured to the upper end of stem 18 is a piston 88 having an area slightly larger than poppet 82 and having at its upper end a seal 98 to prevent escape of fluid. Screwed on the top of housing 14 is a cap 92 compressing a coil spring 94 against piston 88 in a direction to close pop-pet 82. A pin 96 passes through cap 92 and is secured to stem 18 for a manual operation of the poppet 82.

In operation, a hydraulic conduit will be seecured to the left opening 53, and to the right opening 86, and suitable valve means will be provided to direct fluid under pressure to one opening and to connect the other opening to exhaust for operating the cylinder in one direction, or to reverse the fluid pressures and move the piston in the other direction. The cylinder as a whole may be held stationary with respect to the airplane on which it is mounted and the parts desired to be actuated may be connected with the clevises 28 and 34.

When it is desired to move piston IE to the left with respect to cylinder l 0, hydraulic fluid under pressure is directed to opening 86, and opening 53 is connected to exhaust. Since the area of piston 88 is greater than poppet 82, hydraulic pressure will force piston 88 upwardly in the position shown, unseating poppet 82 and lifting lock pin 14 to unlock it from the left side of lockstep 22. Thereafter, the fluid under pressure will flow through passages 16 in pin 14 and operate against piston 16 to force it and the piston rods 32 and 24 to the left. Exhaust fluid will be forced out through passages 58 and will cause poppet 52 to unseat allowing the escape of fluid through opening 53. Spring 66 is relatively weak and the exhaust pressure will cause the piston 60 to be raised upwardly in the position shown in the drawing although this action is not important to the operation of the lock. As the piston l6 nears the end of its stroke moving to the left the lockstep 20 moves into the bore Ml trapping fluid between piston I6 and housing l2. This fluid will be slowly metered around lockstep 20 giving a dashpot action which reduces the A bore is coaxial rate of movement of piston l6 and eliminates any stresses which might otherwise be caused by the impact of a sudden stop. When piston It finall completes its stroke no more exhaust fluid will flow out of passage 56, and spring will force the lock pin 44 downwardly causing it to engage the right hand portion of lockstep 20 thus securely locking the piston 16 from movement in either direction.

v If the parts connected to the clevis 26 and piston rod 24 should now be subjected to sudden impact as for example the landing wheels of an airplane upon landing, this force would be transmitted to the lock pin 44. Lock pin 44 is made relatively close fitting in passage 42, but as there is always some tendency for rotation when resisting an impact shock, the pivot 46 is provided to eliminate the transmission of this rotational movement to the stem 48, the piston 60, and associated parts to prevent injury to them. If the hydraulic system should fail, or for purposes of ground maintenance it is desirable to unlock the lock pin 44, manual pressure may be exerted on the stem 68 to withdraw the pin 44. Stem 68 may also be used in a signaling system to tell the pilot when the wheels are extended or retracted since at the completion of the stroke while pressure is applied, the pin at the exhaust port will be seated and the pin at the inlet port will be raised.

If it should now be desired to cause the piston It to move to the right in cylinder Ill fluid under pressure is directed at .opening 53 and opening 88 is connected to exhaust. The fluid under pressure will act against piston 60 causing it to rise and unseat poppet 52 and unlock pin 44. Thus, it will be apparent that no fluid under pressure can pass into the cylinder until the lock pin 44 is completely disengaged from lockstep 20. This prevents subjecting the lock mechanism to stresses due to the application of hydraulic fluid before the unlatching of the lock mechanism. Thereafter, fluid under pressure will flow down passages 58 and force the piston IE to the right and cause exhaust fluid to flow through passages 76 to opening 86. As piston I6 nears the end of its stroke, moving to the right, lookstep 22 enters passages 10 trapping fluid between piston I6 and the housing I4 and also trapping fluid between lockstep 22 and the hydraulic seals 38.' This trapping of fluid reduces the speed of movement of piston l6 giving a dashpot action. The trapping of fluid in two places gives a double metering action increasing the effectiveness of the structure for dashpot pur poses. When all fluid has been exhausted the pressure will be reduced against piston 88, and spring 94 will force lock pin 14 downwardly looking the cylinder against the left side of lockstep 22. Poppet 82 will then seat, preventing flow .of fluid to the cylinder until stem 16 shall rise to such a point that look pin 14 will first be released.

From the foregoing description it will be apparent that thestructure of locksteps 2E! and 22 are used not only for locking purposes but'for dashpot operations as well, thus a great saving in weight and cost is effected, both highly desirable features in aircraft work. Further, both the lock and the dash-pot are built integrally with the actuating cylinder so that there will be positive alignment of parts and positiveness of operation. The provision of poppets with a lost motion connection in the lock stem insures that no fluid will flow to the actuating cylinder until the lock pins have first been released. The structure shown on the right hand housing It further gives a double metering action for dashpot purposes. Features of the invention include the provision of a pivot mounting for the lock pin shown for pin 4-. and a provision of manual pins for releasing the looks or operating a signal device.

Although the invention has been described with reference to a particular embodiment thereof, it is not limited tothis embodiment nor otherwise except by the terms of the following claims.

I claim:

1. An actuating motor adapted to be operated by fluid under pressure comprising a cylinder, a piston having a piston rod secured thereto, an annular lockstep formed on said piston rod, a housing connected with one end of said cylinder and having a bore coaxial with said piston rod but of lesser diameter than the cylinder and of slightly greater diameter than the lockstep, and a lock pin adapted to lock against said annular lockstep, the clearance between the coaxial bore and the lockstep being such as to form a dashpot metering orifice with respect to the operating fluid.

2. An actuating cylinder adapted to be operated to be operated by fluid under pressure having a combined lock and dashpot comprising, a cylinder housing, a piston and rod assembly therein, a lock projection formed on said assembly, a recess to receive said projection at one end of said cylinder housing to create a dashpot, and a lock pin carried by said cylinder housing adapted to cooperate with said lock projection to lock said piston, the clearance between said projection and said recess being such as to form a metering orifice with respect to the operating fluid.

3. An actuating cylinder adapted to be operated by fluid under pressure comprising a cylinder housing, a piston therein, said piston and housing having cooperating projection and recess means to form a dashpot action, lock means formed in said projection, and lock means in said recess adapted to cooperate with said proiection lock means, the clearance between said projection and said recess being such as to form a metering orifice with respect to the operating fluid.

4. An actuating cylinder having a combined lock and dashpot comprising, a cylinder housing, a piston having a projection with a lock step formed therein, a lock pin on said housing adapted to be projected into said housing to contact said lock step, said housing having a recess adapted to receive said projection, and having an operating passage connected to the remote end of said recess, creating a dashpot by the trapping of fluid between the piston and the cylinder housing.

5. An actuating cylinder having a combined lock and dash comprising, a cylinder housing, a piston having a projection with lock means formed therein, lock means on said housing adapted to cooperate with said piston lock means, said housing having a recess adapted to receive said projection, and having an operating passage connected to a point on said recess intermediate its ends thereby creating a dashpot action in the remote end of said recess and between said piston and said passage.

6. An actuating cylinder having a combined lock and dashpot comprising, a cylinder housing, having a recess at one end, a piston therein having a projection on which is formed a lock step, a hollow lock pin in said housing at the region of said recess adapted to be projected inwardly to contact said lock step, said projection being adapted to fit into said recess to form a dashpot, said hollow lock pin also serving as an opening for fluid ingress and egress to the cylinder.

DAVID H. BROWN. 

